I disagree with the assertion you made about 'freedom'.
When you connect a signal via code, you're free to choose not to create the callback and instead encounter an error when running your code. Doing the exact same thing in the editor will (as of now) force you to create a callback (even though your are free to remove it again). I think that is a sane default, as it prevents beginners from running into an rather obvious error (once you grow accustomed to the use of signals).
It's worth noting that connecting signals via the editor is limited in other ways as well: for example you cannot provide extra arguments to the callback other than by code. That's not to say I like it that way, but connecting a signal from code is undeniably more powerful, expressive and limitless than doing it via the editor as of now.
The question is really just about an editor workflow.
To clarify: I fully support an option to opt-out of the automatic stub-creation! I'd say a toggle (defaulting to true, unless specified otherwise via the - currently not working - flag in the editor settings) in the "Advanced" section of the "Connect..."-dialog would be optimal, benefiting both beginners and advanced users of the engine.